The present invention relates to a water ejector for discharging condensate from such devices as an air tank of an air compressor, an after cooler, a drain separator, an air drier, or a mist separator.
In a conventional air compressor, moisture condensed from the compressed air is normally contaminated with oil and particulates, so it must be kept from entering downstream devices lest they also become contaminated. It is customary to pass the compressed air through drying devices, such as an after cooler, a drain separator, and an air drier, connected in series to remove the moisture, oil, and other contaminants. In some cases, a mist separator may also be included.
Drain discharge valves, which control the flow of liquid from drain pipes, may be any suitable devices, whether mechanical, electromagnetic, or electric (shutter/opening and closing). Automatic operation of drain discharge valves using, for example, electromagnetic valves, is desirable. However, the cost of four electromagnetic valves, one for each device, is quite high. In a conventional system, a single drain discharge valve cannot be substituted for a sequence of such valves because the series connection of the devices induces pressure drops in the downstream direction, whereby air pressure at each drain discharge valve decreases with each valve in the sequence.
In another prior-art embodiment of a drain discharge device, drain discharge outlets are coupled in sequence according to decreasing discharge pressure. Compressed air is fed through a feed pipe to an after cooler, which is at a pressure relatively higher than the air pressure of a drain separator, both of which are coupled to an inlet of a drain discharge valve. A check valve between the drain separator and the drain discharge valve prevents drain discharge effluent from flowing back from the drain discharge valve side to the drain separator side. This drain discharge embodiment reduces system cost by the difference between the price of a drain discharge valve (which is expensive) and the price of a check valve.
The saving is effected through the removal of one of the drain discharge valves in the conventional example described above. However, the check valve may become clogged with particulate foreign matter and thereby lose its ability to function. As a result, drain discharge outlets of the after cooler and the drain separator are effectively coupled together and the discharge of effluent from the drain separator becomes difficult. Further, when the drain discharge valve is open, if the difference in the air pressure between the drain outlet of the after cooler and the drain outlet of the drain separator is small, the viscosity of oil in the drain keeps the check valve from opening despite its inherent preset pressure. Consequently, no effluent can be discharged. Although the number of drain discharge valves can be reduced by adding a plurality of check valves, the greater the number of check valves, the more likely the clogging.